P472: SINGLE-CELL PROFILING REVEALS HETEROGENEITY OF EXPANDED PLASMACYTOID DENDRITIC CELLS IN ACUTE MYELOID LEUKEMIA
Authors: Juan Peng, Xingcheng Yang, Xia Mao, Jue Wang, Jia Wei
Journal: HemaSphere (2023)

Background: Plasmacytoid dendritic cells (pDCs) are a major source of natural type I interferon (IFN-I), and play critical roles in the immune response. Typically, only less than 1% pDC can be detected in the total bone marrow or peripheral blood nuclear cells. Uncontrolled proliferation of transformed pDCs is the most remarkable characteristics of blastic plasmacytoid dendritic cell neoplasm (BPDCN). Recently, abnormal amplification of pDCs in myeloid neoplasms were also been reported in MDS/AML patients (pDC-AML/MDS) and may favor disease progression. Here, we performed retrospective analysis and single-cell RNA-sequencing (scRNA-seq) to investigate the difference of pDCs characteristics between BPDCN and pDC-AML/MDS. Aims: To investigate the pDCs characteristics in pDC-AML/MDS/BPDCN, and to better understand the mechanisms of therapy escape mediated by this specialized type cells. Methods: Retrospective analysis was performed on 31 patients diagnosed with PDC-AML/MDS/BPDCN (1 pDC-MDS, 13 pDC-AML, 17 BPDCN) from Tongji Hospital of Huazhong University of Science and Technology in Wuhan, China from July 2014 to September 2022. scRNA-seq using 10x Genomics platform were performed on bone marrow (BM) samples from 2 pDC-AML patients and 1 BPDCN patient. In addition, we integrated public scRNA-seq data of 5 BPDCN patients and 5 healthy donors BM samples from the publicly available database. Results: The median pDC proportion of pDC-AML/MDS was 7.4% (range 2.7-33.6%), and the proportion of pDCs in patients with BPDCN were mostly below 1%. As of September 2022, The median survival of patients with pDC-MDS/AML was 6 months, no significant difference between BPDCN patients (9 months; P＞0.05). Notably, pDC-AML/MDS patients were insensitive to chemotherapy, that most patients (81%, 9/11) need two or more courses chemotherapy to achieve CR, even though, OS of these patients are poor when compared with patients undergoing HSCT(P＜0.05). To further clarified the role of pDCs in these patients, we performed scRNA-seq and acquired 35,796 cells across all samples (2 pDC-AML, 6 BPDCN, and 5 health donors) following quality control and filtering, and identified 18 clusters in the overall t-SNE map. The differentially expressed genes (DEGs) among pDCs form HDs, pDC-AML and BPDCN patients showed different expression patterns. Between pDC-AML and HDs, 425 DEGs were downregulated and 609 DEGs were upregulated, while between pDC-AML and BPDCN, 1117 DEGs were downregulated and 1077 DEGs were upregulated. To further specify functions of these DEGs, Gene Set Enrichment Analysis (GSEA) were performed, compare with HDs, the pathways of “TGF-β signaling”, “TNF-α signaling via NF-κB”, and “p53 pathway” were upregulated in pDCs from pDC-AML, while the path way of “interferon-α response” was downregulated. These results showed that the pDCs from pDC-AML share similar properties of AML blasts, and cytokines, such as TGF-β and TNF-α are likely to mediates their proliferation. Summary/Conclusion: pDC-AML/MDS/BPDCN showed resistant to chemotherapy. Our study demonstrates large heterogeneity of pDCs between pDC-AML, BPDCN and healthy donors. The heterogeneity in transcriptomic profiles may mediated the resistance.Keywords: Myelodysplastic syndrome, Acute myeloid leukemia, RNA-seq